Field of the Invention
The present invention relates to a zoom lens and an image pickup apparatus including the zoom lens, which are suitably used for an electronic camera such as a video camera or a digital still camera, a film camera, a broadcasting camera, or the like.
Description of the Related Art
For image pickup apparatus in recent years, a compact zoom lens having a high aperture ratio and high optical performance is required. In order to obtain the compact zoom lens, a diameter of a lens barrel needs to be reduced, and there is a need to appropriately set a position of a stop unit in an optical axis direction so that a stop diameter of an aperture stop is reduced.
In order to reduce the stop diameter of the aperture stop while obtaining the high aperture ratio, it is preferred to arrange the aperture stop on an image side of an optical system.
In U.S. Pat. No. 8,189,074, there is disclosed a zoom lens including a first lens unit having a positive refractive power, a second lens unit having a negative refractive power, a third lens unit having a negative refractive power, a lens unit 4A having a positive refractive power, an aperture stop, and a lens unit 4B having a positive refractive power.
According to U.S. Pat. No. 5,691,851, in a zoom lens including, in order from an object side to an image side, a first lens unit to a sixth lens unit having positive, negative, positive, negative, positive, and negative refractive powers, an aperture stop is arranged between the third lens unit and the fourth lens unit.
According to U.S. Pat. No. 8,107,171, in a zoom lens including, in order from an object side to an image side, five lens units having positive, negative, positive, negative, and positive refractive powers, an aperture stop is arranged in the third lens unit.
According to U.S. Pat. No. 8,537,471, in a zoom lens including, in order from an object side to an image side, a first lens unit to a sixth lens unit having positive, negative, positive, positive, negative, and positive refractive powers, an aperture stop is arranged on the image side of the third lens unit or on the image side of the fourth lens unit.